Tag Archives: #glaucoma

Scientists Discover Gene Therapy Which Provides Neuroprotection To Prevent Glaucoma Vision Loss (Medicine)

An NIH-funded research project found that calcium modulator CaMKII protects the optic nerve in mice, opening the door to new sight-saving therapy

A form of gene therapy protects optic nerve cells and preserves vision in mouse models of glaucoma, according to research supported by NIH’s National Eye Institute. The findings suggest a way forward for developing neuroprotective therapies for glaucoma, a leading cause of visual impairment and blindness. The report was published in Cell.

Glaucoma results from irreversible neurodegeneration of the optic nerve, the bundle of axons from retinal ganglion cells that transmits signals from the eye to the brain to produce vision. Available therapies slow vision loss by lowering elevated eye pressure, however some glaucoma progresses to blindness despite normal eye pressure. Neuroprotective therapies would be a leap forward, meeting the needs of patients who lack treatment options.

“Our study is the first to show that activating the CaMKII pathway helps protect retinal ganglion cells from a variety of injuries and in multiple glaucoma models,” said the study’s lead investigator, Bo Chen, Ph.D., associate professor of ophthalmology and neuroscience at the Icahn School of Medicine at Mount Sinai in New York City.

The CaMKII (calcium/calmodulin-dependent protein kinase II) pathway regulates key cellular processes and functions throughout the body, including retinal ganglion cells in the eye. Yet the precise role of CaMKII in retinal ganglion cell health is not well understood. Inhibition of CaMKII activity, for example, has been shown to be either protective or detrimental to retinal ganglion cells, depending on the conditions.

Using an antibody marker of CaMKII activity, Chen’s team discovered that CaMKII pathway signaling was compromised whenever retinal ganglion cells were exposed to toxins or trauma from a crush injury to the optic nerve, suggesting a correlation between CaMKII activity and retinal ganglion cell survival.

Searching for ways to intervene, they found that activating the CaMKII pathway with gene therapy proved protective to the retinal ganglion cells. Administering the gene therapy to mice just prior to the toxic insult (which initiates rapid damage to the cells), and just after optic nerve crush (which causes slower damage), increased CaMKII activity and robustly protected retinal ganglion cells.

Among gene therapy-treated mice, 77% of retinal ganglion cells survived 12 months after the toxic insult compared with 8% in control mice. Six months following optic nerve crush, 77% of retinal ganglion cells had survived versus 7% in controls.

Similarly, boosting CaMKII activity via gene therapy proved protective of retinal ganglion cells in glaucoma models based on elevated eye pressure or genetic deficiencies.

Increasing retinal ganglion cell survival rates translated into greater likelihood of preserved visual function, according to cell activity measured by electroretinogram and patterns of activity in the visual cortex.

Three vision-based behavioral tests also confirmed sustained visual function among the treated mice. In a visual water task, the mice were trained to swim toward a submerged platform on the basis of visual stimuli on a computer monitor. Depth perception was confirmed by a visual cliff test based on the mouse’s innate tendency to step to the shallow side of a cliff. Lastly, a looming test determined that treated mice were more apt to respond defensively (by hiding, freezing or tail rattling) when shown an overhead stimulus designed to simulate a threat, compared with untreated mice.

“If we make retinal ganglion cells more resistant and tolerant to the insults that cause cell death in glaucoma, they might be able to survive longer and maintain their function,” Chen concluded.

This study was supported by NEI grants R01EY028921, R01EY024986. NEI is part of the National Institutes of Health.

Featured image: Graphical abstract by authors


Reference:

Guo X, Zhou J, Starr C, Mohns EJ, Li Y, Chen E, Yoon Y, Kellner CP, Tanaka K, Wang H, Liu W, LR, Demb JB, Crair MC, and Chen B. “Preservation of vision after CaMKII-mediated protection of retinal ganglion cells.” Published online July 22, 2021 in Cell. DOI: https://doi.org/10.1016/j.cell.2021.06.031


Provided by NIH/NEI

MIPT and Harvard Researchers Grow Stem Cells to Cure Glaucoma (Medicine)

A joint research carried out by MIPT scientists and Harvard researchers have presented retinal cells that can integrate into the retina. This is the first successful attempt to transplant ganglion cells (retinal neurons that are destroyed by glaucoma) derived from stem cells in a lab setting. Scientists tested the technology in mice and established that the cells successfully integrated and survived for a year. In the future, the researchers plan to create specialized cell banks, which will permit individual, tailored therapy for each patient. The paper was published in Molecular Therapy – Methods and Clinical Development.

The world’s first successful attempt to grow and transplant retinal ganglion cells developed from stem cells was made by scientists from MIPT’s genomic engineering laboratory in collaboration with researchers from Harvard Medical School. Retinal ganglion cells, commonly damaged in glaucoma, are responsible for the transmission of visual information. The scientists managed to not only grow neurons (retinal ganglion cells are considered specialized neurons), but also transplant them into the eyes of mice, achieving the correct ingrowth of artificial retinal tissue. Without treatment, glaucoma can lead to irreversible damage to the optic nerve and, as a result, the loss of part of the visual field. Progression of this disease can lead to complete blindness.

Retinal cells were grown using special organoids, with the tissue formed in a petri dish, according to Evgenii Kegeles, a junior researcher from MIPT’s genomic engineering laboratory. These cells were subsequently transplanted into several groups of mice. The MIPT scientists were responsible for re-isolating and analyzing the transplanted cells. 

“Our studies in mice have shed light on some of the basic questions surrounding retina cell replacement, i.e. can donor RGCs survive within diseased host retinas? Or are transplants only possible within young hosts?”, noted Julia Oswald, the first author of the paper and a research fellow from the Schepens Eye Research Institute, Harvard Medical School affiliate. “Using mice in which we used microbeads to artificially elevate intraocular pressure and a model of chemically induced neurotoxicity, we could show that transplanted donor cells survive in disease-like microenvironments. In addition, we could demonstrate that cells survived independent of the donor’s age and the location to which the cells were delivered within the retina.”  

According to the authors, these cells have successfully existed inside mouse retinas for 12 months, which is a significant period for the species. Scientists confirmed that they were able to receive signals from other neurons in the retina; however, the ability of the cells to transmit signals to the brain has yet to be assessed with absolute certainty.

“We are confident that the grown cells are embedded where necessary and have extended axons into the brain, but their full functionality is currently impossible to assess, due to the relatively low number of cells surviving the procedure. However, our study shows a first proof-of-concept for the re-isolation of donor cells post-transplant, to observe on a molecular level that cells did, indeed, form synapses, grow axons, and integrate into the retina. This technique will enable countless future studies into the cross talk between transplanted cells and the host microenvironment. This will allow us to find and employ molecular mechanisms which will help transplanted cells to function properly and, as a result, improve visual function when transplanted in the right quantity,” explained Evgenii Kegeles.

Mouse retinal cells can be grown from stem cells in around 21 days. However, according to the scientists at MIPT, it will take longer for human cells — from 50 to 100 days. 

Even so, a person with glaucoma preparing for a transplant will most likely not require retinal tissue grown from their own autologous stem cells. Since the eye is an immune-privileged organ where rejection is rare, it is possible to create a cell bank for these patients; grown retinal cells from a universal donor or induced pluripotent stem cells would be stored there. This would mean that it would be possible to grow cells in advance and freeze them. When a patient with glaucoma requires help, the most suitable cells would be selected for transplantation. 

“The Nobel Prize for induced pluripotent stem cells was awarded almost 10 years ago, in 2012,” said Pavel Volchkov, head of the laboratory of genomic engineering. “The so-called hype, when literally all of the research teams involved in the process considered it their duty to explore the topic, has long faded away. Now is the time not just for words, but for real technologies based on iPS (induced pluripotent stem cells). And it is precisely this technology that this research on the transplantation of retinal ganglion cells is based on. This is an opportunity to demonstrate that stem cells can really be applied in practice, that, with their help, something can be corrected. Although this work has not yet been brought to clinical practice, it is only a few steps away from a real transplant for the purpose of treating glaucoma.”

“It was indeed an enabling study in which we demonstrated that it is possible to make diverse retinal ganglion cell neurons in quantity sufficient for transplantation. Moreover, donor neurons’ ability to integrate into the diseased retina and survive for over a year brings hope and excitement for cell therapy development,” – added Petr Baranov, – the Principal Investigator from the Schepens Eye Research Institute, Harvard Medical School.

According to scientists, this technology is around 10 years from being ready for use in clinical practice.

___

Header Photo. Stem cells on the retinal surface by 2 weeks post transplantation. Credit: Molecular Therapy – Methods and Clinical Development.


Reference: Julia Oswald et al., “Transplantation of miPSC/mESC-derived retinal ganglion cells into healthy and glaucomatous retinas”, vol. 21, pp. 180-198, 2021. DOI: https://doi.org/10.1016/j.omtm.2021.03.004


Provided by MIPT

Glaucoma may be more than just an issue of eye pressure

A chemical known to protect nerve cells also slows glaucoma, the leading cause of irreversible blindness, results of a new study in rats show.

Led by researchers at NYU Grossman School of Medicine, the study centers on the watery fluid inside the eye on which its function depends. Fluid pressure can build up in patients with glaucoma, wearing down cells in the eye and the nerves connecting them to the brain, researchers say.

However, past studies have shown the condition to continue to worsen even after eye pressure has been controlled. The connection between pressure buildup and impaired vision remains poorly understood.

Publishing April 13 in Neurotherapeutics, the new study showed that ingesting the compound citicoline restored optic nerve (neural) signals between the brain and eye to near-normal levels in the study rats. Naturally produced in the brain but also available commercially, citicoline is a major source of choline, a building block in the membranes that line nerve cells and enhance nerve cell communication.

While the study results confirmed past findings that elevated eye pressure contributes to nerve damage in glaucoma, it also showed that citicoline reduced vision loss in rats without reducing fluid pressure in the eye.

“Our study suggests that citicoline protects against glaucoma through a mechanism different from that of standard treatments that reduce fluid pressure,” says senior study author Kevin Chan, PhD, an assistant professor in the Department of Ophthalmology at NYU Langone Health. “Since glaucoma interrupts the connection between the brain and eye, we hope to strengthen it with new types of therapies.”

According to the National Glaucoma Foundation, over 3 million Americans have glaucoma, but only half know they actually have it. In the US, more than 120,000 individuals are blind from the disease. In addition, the World Health Organization estimates that over 60 million individuals suffer from glaucoma worldwide.

The findings are helping scientists better understand how glaucoma works and add to past evidence that citicoline may counter the disease, says Chan, also the director of the Neuroimaging and Visual Science Laboratory at NYU Langone. Previous studies had showed that humans and rodents with glaucoma have lower than normal levels of choline in the brain. Until now, Chan says, there’s been little concrete evidence of the effectiveness of choline supplements as a therapy for glaucoma or why choline occurs in lower levels in glaucoma patients.

Chan and his team tested whether increasing levels of that chemical would slow or even stop the degradation of the optic nerve and other regions of the brain involved in vision. Using a comprehensive study of the eye-brain connection in glaucoma, his team found that giving rats oral doses of citicoline over a three-week period protected nerve tissues and reduced vision loss sustainably even after the treatment stopped for another three weeks.

For the study, the researchers simulated glaucoma in several dozen rats using a clear gel to build up eye pressure mildly without otherwise blocking their vision. Then, the team measured the structural integrity and the amount of functional and physiological activity along the visual pathway using MRI scanning. The researchers also tracked the rodents’ visual behavior to test the clarity of vision of each eye.

The study showed that for rats with mildly elevated eye pressure, the tissues that connect the eye and brain, including the optic nerve, decayed for up to five weeks after the injury occurred. Meanwhile, nerve structure breakdown in the citicoline-treated rodents slowed by as much as 74 percent, which indicated that the chemical had protective effects on nerve cells, say the authors.

The researchers caution that more research is needed before turning to citicoline supplements to treat glaucoma in humans, as commercial drugs have yet to be proven fully effective in clinical trials. Moving forward, the researchers plan to investigate the origin of choline decline in people with glaucoma as well as how citicoline works to repair the damage.

Funding for the study was provided by National Institutes of Health grant R01 EY028125, a Liesegang Fellowship, a Research to Prevent Blindness/Stavros Niarchos Foundation International Research Collaborators Award; and an Unrestricted Grant from Research to Prevent Blindness to NYU Langone Health’s Department of Ophthalmology.

In addition to Chan, other NYU Langone researchers included Jeffrey R. Sims, BS; Gadi Wollstein, MD; and Joel S. Schuman, MD. Other researcher support was provided by Yolandi van der Merwe, PhD; Matthew C. Murphy, PhD; Xiao-Ling Yang, MD; Leon C. Ho, PhD; and Ian P. Conner, MD, PhD, at the University of Pittsburgh. Yu Yu, PhD, at Hong Kong University of Science and Technology in Hong Kong, and Christopher K. Leung, MD, at the Chinese University of Hong Kong provided further research support.


Reference: van der Merwe, Y., Murphy, M.C., Sims, J.R. et al. Citicoline Modulates Glaucomatous Neurodegeneration Through Intraocular Pressure-Independent Control. Neurotherapeutics (2021). https://link.springer.com/article/10.1007/s13311-021-01033-6 https://doi.org/10.1007/s13311-021-01033-6


Provided by NYU Langone

Smartphones Could Help To Prevent Glaucoma Blindness (Medicine)

Smartphones could be used to scan people’s eyes for early-warning signs of glaucoma – helping to prevent severe ocular diseases and blindness, a new study reveals.

Some of the most common eye-related diseases are avoidable and display strong risk factors before onset, but it is much harder to pinpoint a group of people at risk from glaucoma.

Glaucoma is associated with elevated levels of intraocular pressure (IOP) and an accurate, non-invasive way of monitoring an individual’s IOP over an extended period would help to significantly increase their chances of maintaining their vision.

Soundwaves used as a mobile measurement method would detect increasing values of IOP, prompting early diagnosis and treatment.

Scientists at the University of Birmingham have successfully carried out experiments using soundwaves and an eye model, publishing their findings in Engineering Reports.

Co-author Dr. Khamis Essa, Director of the Advanced Manufacturing Group at the University of Birmingham, commented: “We discovered a relationship between the internal pressure of an object and its acoustic reflection coefficient. With further investigation into eye geometry and how this affects the interaction with soundwaves, it is possible to use a smartphone to accurately measure IOP from the comfort of the user’s home.”

Risk factors for other eye diseases are easier to assess – for example, in the case of diabetic retinopathy, individuals with diabetes are specifically at risk and are constantly monitored for tiny bulges that develop in the blood vessels of the eye.

The current ‘gold standard’ method of measuring IOP is applanation tonometry, where numbing drops followed by non-toxic dye are applied to the patient’s eyes. There are problems and measurement errors associated with this method.

An independent risk factor of glaucoma is having a thin central corneal thickness (CCT) – either by natural occurrence or a common procedure like laser eye surgery.

A thin CCT causes artificially low readings of IOP when using applanation tonometry. The only way to verify the reading is by a full eye examination – not possible in a mobile situation. Also, the equipment is too expensive for most people to purchase for long-term home monitoring.

IOP is a vital measurement of healthy vision, defined as pressure created by continued renewal of eye fluids. Ocular hypertension is caused by an imbalance in production and drainage of aqueous fluid – most common in older adults. Risk increases with age, in turn increasing the likelihood of an individual developing glaucoma.

Glaucoma is a disease of the optic nerve which is estimated to affect 79.6 million people world-wide and, if left untreated, causes irreversible damage. In most cases, blindness can be prevented with appropriate control and treatment.

Featured image: Some of the most common eye-related diseases are avoidable © University of Birmingham


Reference: ‘Testing the viability of measuring intraocular pressure using soundwaves from a smartphone’ – Matthew Soanes, Khamis Essa and Haider Butt – is published in Engineering Reports. Read the research paper.


Provided by University of Birmingham

International Team Identifies 127 Glaucoma Genes in Largest Study of its Kind (Medicine)

Researchers for the first time analyzed genes in more than 34,000 people with glaucoma across multiple ancestries and found 44 new genetic variants that may lead to new treatment targets.

In the largest genome-wide association study of glaucoma comparing the genes of 34,179 people with the disease to 349,321 control subjects, an international consortium of researchers identified 44 new gene loci and confirmed 83 previously reported loci linked to glaucoma. Loci are considered “genetic street addresses,” denoting a specific location on a gene.

The study’s authors hope the identification of these genes will lead to new treatment targets for this incurable eye disease that is a leading cause of blindness worldwide.

“These new findings come out of the highest-powered genome-wide association study of glaucoma to date, and show the power of team science and using big data to answer questions when research groups around the world join forces,” said co-senior study author Janey L. Wiggs, MD, PhD, Associate Chief of Ophthalmology Clinical Research at Mass Eye and Ear, and the Paul Austin Chandler Professor of Ophthalmology and Vice Chair of Clinical Research at Harvard Medical School. “The number of genes identified will lead to the discovery of new biological pathways that can lead to glaucoma, and in turn, new targets for therapeutics,” added Dr. Wiggs, the Associate Director of the Ocular Genomics Institute at Harvard Medical School and a member of the National Academy of Medicine.

The findings were published February 24 in Nature Communications.

Glaucoma affects more than 75 million individuals worldwide, including about 3 million people in the United States, and these numbers are expected to increase with the aging population. Glaucoma causes irreversible damage to the eye’s optic nerve. This damage is often painless and hard to detect as it begins, but over time can lead to vision loss. Primary open angle glaucoma is one of its most common forms of the disease and is highly hereditary, but the genes involved in the disease have been poorly understood.

First cross-ancestry comparison of glaucoma genes

For the first time in a glaucoma genome-wide association study, a cross-ancestry comparison was performed looking at genetic data from people of European, African and Asian descent. The researchers found the majority of loci that contribute to glaucoma were consistent across all three groups. Previous studies had mostly looked at gene data from people of European descent.

“Glaucoma rates are highest in African and Asian ancestry groups, but the largest genetic studies of glaucoma in the past focused on people of European ancestry,” said lead author Puya Gharahkhani, Associate Professor in the Statistical Genetics group at QIMR Berghofer Medical Research Institute in Australia. “Those studies showed genetic tests could be used to help identify who would benefit from sight-saving early monitoring or treatment, but because of the narrow scope of the genetic data, we weren’t sure until now that the genetic indicators were true for people of different ancestries.

The cross-ancestry data improved fine-mapping of causal variants linked to glaucoma. By integrating multiple lines of genetic evidence, the researchers implicated previously unknown biological processes that might contribute to the development of the disease.

Genetic findings may lead to better testing and clinical trial targets

Future initiatives for the research group will focus on using these genetic loci to improve screening and diagnosis of glaucoma, and one day, to develop new treatments.

Previous studies from the group used genes identified to develop polygenic risk scores, which are estimates of a person’s disease risk. This new study can add a larger collection of genetic variants to improve this risk score’s specificity. Such information can be important for screening patients who might be at risk for glaucoma, and for allowing patients with glaucoma to better understand their disease course based on their genetic profile. Studies are planned to identify how patients at higher genetic risk fare clinically, such as determining if polygenic risk score is linked to a need for eye drops or surgery.

Another future avenue for the research is identifying new causal genes and mechanisms for glaucoma, and using that information to develop therapeutic approaches to target those genes. The risk loci identified include genes that are highly expressed in relevant eye tissues, nerves, arteries and other tissues related to glaucoma.

Current glaucoma treatments are aimed at reducing eye pressure in order to slow the disease’s progression and prevent permanent damage to the optic nerve, however no treatment can stop or cure glaucoma. While some current clinical trials are looking at treatments for certain genes, these new findings might increase the amount of targets and more precise treatments.

“Glaucoma is one of the most strongly genetic human diseases, which is why we are looking at the genetic architecture of the disease to find clues on how to prevent and treat it,” said Professor Stuart MacGregor, the head of QIMR Berghofer’s Statistical Genetics group and co-senior researcher on the study. “We’re hopeful that understanding the biological processes and knowing which genes control them could help scientists develop new drugs in the future.”

The research was an international effort that included researchers from Australia, the United Kingdom, The Netherlands, Finland, Germany, Singapore, Japan, Nigeria, Ghana, South Africa, Switzerland, Tanzania and the United States. The research included samples from the U.S.-based NEIGHBORHOOD consortium, a National Eye Institute collaborative research effort led by principal investigator, Dr. Wiggs. This new study included 10 times more glaucoma cases and controls included than an earlier study from the group.

The NEIGHBORHOOD consortium receives funding support from the National Eye Institute (NEI) of the National Institutes of Health (NIH) (P30 grants EY014104, R01 EY015473, and R01 EY022305).

In addition to Dr. Wiggs, a Mass Eye and Ear co-author on the paper is Ayellet V. Segrè, PhD, a genetic biostatistician and Assistant Professor and member of the Ocular Genomics Institute at Harvard Ophthalmology.

Featured image: This figure summarizes the four stages of this study, as well as the data resources and main analyses/results for each stage. © Gharahkhani et al.


Reference: Gharahkhani, P., Jorgenson, E., Hysi, P. et al. Genome-wide meta-analysis identifies 127 open-angle glaucoma loci with consistent effect across ancestries. Nat Commun 12, 1258 (2021). https://www.nature.com/articles/s41467-020-20851-4 https://doi.org/10.1038/s41467-020-20851-4


Provided by Massachusetts Eye and Ear Infirmary

A Rift in the Retina May Help Repair the Optic Nerve (Neuroscience)

In experiments in mouse tissues and human cells, Johns Hopkins Medicine researchers say they have found that removing a membrane that lines the back of the eye may improve the success rate for regrowing nerve cells damaged by blinding diseases. The findings are specifically aimed at discovering new ways to reverse vision loss caused by glaucoma and other diseases that affect the optic nerve, the information highway from the eye to the brain.

Transplanted retinal ganglion cells marked with a fluorescent tag. Credit: Thomas Johnson and Johns Hopkins Medicine

“The idea of restoring vision to someone who has lost it from optic nerve disease has been considered science fiction for decades. But in the last five years, stem cell biology has reached a point where it’s feasible,” says Thomas Johnson, M.D., Ph.D., assistant professor of ophthalmology at the Wilmer Eye Institute at the Johns Hopkins University School of Medicine.

The research was published Jan. 12 in the journal Stem Cell Reports.

A human eye has more than 1 million small nerve cells, called retinal ganglion cells, that transmit signals from light-collecting cells called photoreceptors in the back of the eye to the brain. Retinal ganglion cells send out long arms, or axons, that bundle together with other retinal ganglion cell projections, forming the optic nerve that leads to the brain.

When the eye is subjected to high pressure, as occurs in glaucoma, it damages and eventually kills retinal ganglion cells. In other conditions, inflammation, blocked blood vessels, or tumors can kill retinal ganglion cells. Once they die, retinal ganglion cells don’t regenerate.

“That’s why it is so important to detect glaucoma early,” says Johnson. “We know a lot about how to treat glaucoma and help nerve cells survive an injury, but once the cells die off, the damage to someone’s vision becomes permanent.”

Johnson is a member of a team of researchers at the Johns Hopkins Wilmer Eye Institute looking for ways scientists can repair or replace lost optic neurons by growing new cells.

In the current study, Johnson and his team grew mouse retinas in a laboratory dish and tracked what happens when they added human retinal ganglion cells, derived from human embryonic stem cells, to the surface of the mouse retinas. They found that most of the transplanted human cells were unable to integrate into the retinal tissue, which contains several layers of cells.

“The transplanted cells clumped together rather than dispersing from one another like on a living retina,” says Johnson.

However, the researchers found that a small number of transplanted retinal cells were able to settle uniformly into certain areas of the mouse retina. Looking more closely, the areas where the transplanted cells integrated well aligned with locations where the researchers had to make incisions into the mouse retinas to get them to lie flat in the culture dish. At these incision points, some of the transplanted cells were able to crawl into the retina and integrate themselves in the proper place within the tissue.

“This suggested that there was some type of barrier that had been broken by these incisions,” Johnson says. “If we could find a way to remove it, we may have more success with transplantation.”

It turns out that the barrier is a well-known anatomical structure of the retina, called the internal limiting membrane. It’s a translucent connective tissue created by the retina’s cells to separate the fluid of the eye from the retina.

After using an enzyme to loosen the connective fibers of the internal limiting membrane, the researchers removed the membrane and applied the transplanted human cells to the retinas. They found that most of the transplanted retinal ganglion cells grew in a more normal pattern, integrating themselves more fully. The transplanted cells also showed signs of establishing new nerve connections to the rest of the retinal structure when compared with retinas that had intact membranes.

“These findings suggest that altering the internal limiting membrane may be a necessary step in our aim to regrow new cells in damaged retinas,” says Johnson.

The researchers plan to continue investigating the development of transplanted retinal ganglion cells to determine the factors they need to function once integrated into the retina.

Other researchers involved in the study include Kevin Zhang, Caitlyn Tuffy, Joseph Mertz, Sarah Quillen, Laurence Wechsler, Harry Quigley and Donald Zack of the Johns Hopkins University School of Medicine.

This work was funded by the National Eye Institute (K12EY015025, K08EY031801, R01EY002120, P30EY001765), the ARVO Dr. David L. Epstein Award, Research to Prevent Blindness, the American Glaucoma Society, the Johns Hopkins Physician Scientist Training Program, and generous gifts from the Guerrieri Family Foundation, the Gilbert Family Foundation, and the Marion & Robert Rosenthal Family Foundation.

Reference: Kevin Y. Zhang, Caitlyn Tuffy, Joseph L. Mertz, Sarah Quillen, Laurence Wechsler, Harry A. Quigley, Donald J. Zack, Thomas V. Johnson, Role of the Internal Limiting Membrane in Structural Engraftment and Topographic Spacing of Transplanted Human Stem Cell-Derived Retinal Ganglion Cells, Stem Cell Reports, Volume 16, Issue 1, 2021, Pages 149-167, ISSN 2213-6711, https://doi.org/10.1016/j.stemcr.2020.12.001. (http://www.sciencedirect.com/science/article/pii/S2213671120304951)

Provided by Johns Hopkins Medicine

A Niche For the Eye (Biology)

What if the degenerative eye conditions that lead to glaucoma, corneal dystrophy, and cataracts could be detected and treated before vision is impaired? Recent findings from the lab of Investigator Ting Xie, PhD, at the Stowers Institute for Medical Research point to the ciliary body as a key to unlocking this possibility.

Adult mouse eye Morphology. Image: Courtesy of Xie Lab.

Previous work from the lab showed that when mouse stem cells were differentiated into light-sensing photoreceptor cells in vitro, and then transplanted back into mice with a degenerative condition of the retina, they could partially restore vision. However, the transplanted photoreceptors only lasted three to four months.

“You cannot cure the condition in a diseased eye if you don’t know what causes the disease,” says Xie. “This has been a major hurdle for stem cell therapy in treating degenerative diseases.”

To this end, Xie’s group began to study the eye tissue microenvironment, specifically a specialized tissue in the eye called the ciliary body. Located at the posterior edge of the iris, it is known to maintain ocular pressure by secreting aqueous humor, the clear fluid between the lens and the cornea. It has a similar function in mice and in humans, and defects in the ciliary body manifest in similar ways in the mouse and human eye.

“People think the ciliary body is boring,” says Xie. This might be because the ciliary body was once thought to have a reserve of retinal stem cells, Xie explains, which turned out not to be true. However, its role in eye biology turns out to be quite broad, and “without a functioning ciliary body, the eye degenerates,” Xie adds.

When the Notch signaling pathway—an important cell signaling system found across the animal kingdom—is defective in the ciliary bodies of newly born mice, they fail to develop folds, and secretions decrease, leading to shrunken vitreous bodies. In adult mice, defects in Notch signaling cause low eye pressure, a shrunken vitreous, and eye degeneration. Inactivation of the downstream transcription factor RBPJ in the ciliary body also leads to the same effects. Before now, the underlying molecular mechanism for this outcome was unclear.

In a paper published in Cell Reports on January 12, 2021, first author Ji Pang, a visiting PhD student from Shanghai Jiao Tong University, China, and others describe a signaling pathway wherein Notch and Nectin proteins in the ciliary body function in the development and maintenance of eye tissue and structure.

In this report, the researchers describe the roles of adhesion protein Nectin1 and gap junction protein Connexin43 in the ciliary body of mice. They found that Notch2/3-Rbpj signaling in the outer ciliary epithelium controls the expression of Nectin1, which works with Nectin3 in the inner ciliary epithelium to keep the two tissue layers together, which promotes proper folding of the ciliary body. They found that Notch signaling also maintains the expression of Connexin43 in the outer ciliary epithelium, while Nectin1 localizes and stabilizes Connexin43 on the lateral surface, which maintains the vitreous body and intraocular pressure.

Graphical abstract by  Xie Lab.

Lastly, the researchers found that in addition to maintaining ocular pressure and directing ciliary body morphogenesis, Notch2/3-Rbpj signaling in the inner ciliary epithelium also regulates the secretion of various proteins such as Opticin and collagens into the vitreous body, providing nutritive support for the cornea, the lens, and the retina.

“We propose the ciliary body could be a niche for the eye tissues,” explains Xie, in the sense that it can behave like a stem cell niche, by providing signals that affect cellular morphogenesis and function. “The next important question is what other protein factors secreted by the ciliary body are important for maintaining the cornea, the lens, and the retina, respectively. Some of these factors could be involved directly in eye diseases.”

Other coauthors of the study included Liang Le, PhD, Yi Zhou, PhD, Renjun Tu, PhD, Qiang Hou, PhD, Dai Tsuchiya, PhD, Nancy Thomas, Yongfu Wang, PhD, Zulin Yu, PhD, Richard Alexander, Marina Thexton, Brandy Lewis, Timothy Corbin, Michael Durnin, and Hua Li, PhD, from Stowers; Ruth Ashery-Padan, PhD, from Tel Aviv University, Israel; and Deyue Yan, PhD, from Shanghai Jiao Tong University, China.

This work was supported by the Stowers Institute for Medical Research, the National Eye Institute of the National Institutes of Health (award R01EY027441 to TX), and a China National Scholarship (JP). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Lay Summary of Findings

One of the leading causes of glaucoma is high intraocular pressure, which can cause blindness due to damage of the optic nerve. Intraocular pressure is largely maintained by the ciliary body, a specialized tissue in the eye of animals that secretes fluids. It also functions to maintain structural integrity of the eye, but detailed mechanisms of how it does so had not yet been described.

In a study published online January 12, 2021, in Cell Reports, researchers at the Stowers Institute for Medical Research from the laboratory of Ting Xie, PhD, and collaborators describe how the Notch pathway regulates the secretion of proteins important for supporting eye structure, and also controls the expression of adhesion proteins Nectin1 and Nectin3 to promote the normal structural development of the ciliary body. They find that Nectin proteins ensure expression of the gap junction protein Connexin43, which functions to ensure proper fluid secretion. This work highlights the broad role of the ciliary body in maintenance of eye health and implicates the ciliary body in various eye diseases.

Reference: Ji Pang, Liang Le, Yi Zhou et al., “NOTCH Signaling Controls Ciliary Body Morphogenesis and Secretion by Directly Regulating Nectin Protein Expression”, Cell Reports, 34(2), 2021. https://www.cell.com/cell-reports/fulltext/S2211-1247(20)31592-8 https://doi.org/10.1016/j.celrep.2020.108603

Provided by Stowers Institute for Medical Research

About the Stowers Institute for Medical Research

The Stowers Institute for Medical Research is a non-profit, basic biomedical research organization dedicated to basic research – the critical first step in the quest for new medical diagnostics, therapies and treatments. Jim Stowers, founder of American Century Investments, and his wife, Virginia, opened the Institute in 2000. Since then, the Institute has spent over one billion dollars in pursuit of its mission.

Currently, the Institute is home to about 500 researchers and support personnel, over 20 independent research programs, and more than a dozen technology development and core facilities. Learn more about the Institute at www.stowers.org and about its graduate program at www.stowers.org/gradschool.

Birmingham Research Paves the Way for New Anti-fibrotic Therapy for Glaucoma (Medicine)

Scientists at the University of Birmingham, UK, have shown that a novel low molecular weight dextran-sulphate, ILB® could play a key role in treating open angle glaucoma (OAG), a neurodegenerative disease that affects over 70 million people worldwide and causes irreversible blindness.

Open Angle Glaucoma affects over 70m people worldwide © University of Birmingham

OAG develops slowly over many years. Excessive matrix deposition (fibrosis) within the eye’s main fluid drainage site can lead to increased intraocular pressure (IOP), resulting in damage to the optic nerve.[1]

The research, reported in npj Regenerative Medicine, has shown that that ILB can normalise matrix deposition inside the eye and lower IOP in a pre-clinical model used to mimic these aspects of human glaucoma, paving the way for new anti-fibrotic therapies to be developed for the disease.

OAG is a complex disease and it has proved difficult to develop effective therapeutics to target the biochemical pathways involved. Existing therapies mainly work by reducing fluid production in the eye, not the underlying causes, and even the newer therapies have shown limited success in the clinic.[2]

The Birmingham scientists focussed on an inflammatory pathway that is common to several diseases, and involves Transforming Growth Factor β (TGFβ), a signalling molecule that communicates between cells and orchestrates both inflammation and fibrosis. TGFβ’s role in OAG is well known, with patients demonstrating higher levels in their aqueous humour and laboratory studies showing that artificially increasing TGFβ within the eye can lead to fibrosis [3,4].

The scientists found that ILB has multimodal actions across many genes that resolve inflammatory and fibrotic cellular processes. When they progressed their work into a pre-clinical experimental model of glaucoma, they found that daily subcutaneous injections of ILB significantly (p<0.01) reduced extracellular matrix levels within the eye’s main drainage site, normalised the eye’s pressure and prevented degeneration of retinal neurons. The research was conducted by Dr Lisa Hill, from the Institute of Clinical Sciences, and Dr Hannah Botfield, from the Institute of Inflammation and Ageing. They commented: “We are truly excited by these results, which show a way forward for a glaucoma treatment that can reverse the fibrotic process that causes the disease.”

Clinicians working in ophthalmology generally prefer local over systemically delivered therapeutics, as it is a safer route of administration that is more acceptable to patients.

Dr Hill is leading a project to formulate a topical alternative that will avoid the need for injection. She is working closely on this with Mr Imran Masood, a consultant ophthalmic surgeon at Sandwell and West Birmingham NHS Trust and Professor Liam Grover, a biomaterials expert from the University’s Healthcare Technologies Institute, to assess the use of a novel shear thinning fluid gel for the resolution of glaucoma.

The shear thinning fluid gel was developed for use as eye drops that are retained for an extended period of time following administration, and patents have been filed for its use both alone, and in combination with other therapeutics.[5] Previous studies have shown the fluid gel reduces corneal scarring when applied topically, and it is an effective carrier molecule for other therapeutics.[6]

References:

  1. Tektas, O. Y. & Lutjen-Drecoll, E. Structural changes of the trabecular meshwork in different kinds of glaucoma. Experimental Eye Research, 88(4), 769-75 (2009).
  2. Friedman, S. L., Sheppard, D., Duffield, J. S. & Violette, S. Therapy for fibrotic diseases: Nearing the starting line. Science Translational Medicine 5(167), 167sr1-sr1 (2013).
  3. Fuchshofer, R. & Tamm, E. R. The role of TGF-beta in the pathogenesis of primary open-angle glaucoma. Cell and Tissue Research, 347(1), 279-90 (2012).
  4. Kim, K. S., Lee, B. H. & Kim, I. S. The measurement of fibronectin concentrations in human aqueous humor. Korean Journal of Ophthalmology, 6(1), 1-5 (1992).
  5. Patent numbers: WO/2020/115510; WO/2020/115508; GB2008919.9
  1. Hill et al. Sustained release of decorin to the surface of the eye enables scarless corneal regeneration. npj Regenerative Medicine. 3, 1-12 (2018).
  2. Hill, L.J., Botfield, H.F., Begum, G. et al. ILB® resolves inflammatory scarring and promotes functional tissue repair. npj Regen Med 6, 3 (2021). https://www.nature.com/articles/s41536-020-00110-2 https://doi.org/10.1038/s41536-020-00110-2

Provided by University of Birmingham

Cataract Surgery In Infancy Increases Glaucoma Risk (Ophthalmology)

Children who undergo cataract surgery as infants have a 22% risk of glaucoma 10 years later, whether or not they receive an intraocular lens implant. The findings come from the National Eye Institute (NEI)-funded Infant Aphakic Treatment Study, which today published 10-year follow-up results in JAMA Ophthalmology.

The meshwork and angle are structures that allow fluid to exit the eye, as shown. Scientists speculate that surgery to remove the cataract interferes with the maturation of this “drainage” system that removes fluid from the infant’s eye, leading to increased eye pressure and damage to the child’s eye. Credit: National Eye Institute

“These findings underscore the need for long-term glaucoma surveillance among infant cataract surgery patients. They also provide some measure of assurance that it is not necessary to place an intraocular lens at the time of cataract surgery,” said Michael F. Chiang, M.D., director of NEI.

“The results challenge the notion that replacing the child’s lens with an implanted one protects the child from developing glaucoma, a belief among some pediatric ophthalmology surgeons,” said the trial’s principal investigator, Scott R. Lambert, M.D., professor of ophthalmology at Stanford University, Palo Alto, California.

At the time of cataract removal, the 114 study participants (ages 1-6 months) had been born with cataract in one eye. In the operating room, the infants were randomly assigned to receive an artificial lens implant or go without a lens, a condition called aphakia.

Annually, fewer than 2,500 children in the U.S. are born with cataract, a clouding of the eye’s lens. Surgery is used to remove and replace the cloudy lens. To allow the child’s eye to focus light properly following removal of the cataract, an intraocular lens implant may be placed at surgery, or the eye may be left aphakic, and a contact lens (or glasses, if both eyes have had a cataract removed) may be used to provide the needed correction.

“I tell patients’ parents that implanting a lens in the infant’s eye is like buying your child’s wedding shoes when they’re an infant. It is hard to predict what final power the intraocular lens should have, without knowing how that eye will grow over the years, so placing a lens at the time of cataract removal in an infant involves estimation, and may not turn out to be correct. Hence the eye may end up needing strong glasses or even replacement of the original lens implant.,” said the lead author on the paper, Sharon F. Freedman, M.D., a pediatric glaucoma specialist at Duke University, Durham, North Carolina.

Children who undergo cataract removal have an increased risk of glaucoma, a sight-threatening condition that damages the optic nerve—the connection between the eye and brain. Scientists speculate that surgery to remove the cataract interferes with the maturation of how fluid flows out of the infant’s eye leading to increased eye pressure and optic nerve damage in some of these eyes.

Among the 110 children who were available for re-examination at 10 years, 25 eyes (24%) had developed glaucoma, and 21 eyes (20%) were glaucoma suspects due to elevated eye pressure. However, visual acuity was similar among those eyes that developed glaucoma compared to those eyes that had not. The researchers found no evidence of glaucoma-related eye damage, assessed by imaging of the optic nerve head to measure the retinal nerve fiber layer thickness.

The investigators attribute the absence of glaucoma-related eye damage to close patient monitoring, as any sign of glaucoma was aggressively treated.

While the lifetime glaucoma risk trajectory for patients who have cataract removal as infants remains unknown, this study found that the risk of glaucoma after cataract removal rose from 9% at 1 year, to 17% at 5 years, and to 22% at 10 years.

“Any child who has had a cataract removed needs to be seen by an eye care provider once a year at a minimum,” said Freedman. “Any child diagnosed with glaucoma or above-normal intraocular pressure without signs of ocular damage—what we called glaucoma suspect—should be monitored every four to six months depending upon the stability of the condition and the health of the eye.”

At 10 years, 40% of the followed children had developed the diagnosis of glaucoma or glaucoma suspect. A glaucoma suspect is an eye that has above normal eye pressure or another feature suspicious but not diagnostic of glaucoma.

The findings also confirm that the timing of cataract surgery is a balancing act: Whereas surgery at younger ages increases glaucoma risk, delaying surgery increases risk of amblyopia, a leading cause of visual impairment in children that results when cataract in one eye causes the brain to ignore signals from that eye and favor the other eye.

Future studies of glaucoma following cataract surgery in children will benefit from groundwork by the Infant Aphakic Treatment Study. Freedman said collaboration among the 12 study centers defined diagnostic standards for pediatric glaucoma and glaucoma suspect and criteria for glaucoma-related adverse events. “This cohort began the process leading to an international classification of childhood glaucoma in 2013 that is used around the world today,” she said.

References: Freedman, SF; Beck, AD; Nizam, A; Vanderveen, DK; Plager, DA; Morrison, DG; Drews-Botsch, CD; Lambert, SR; The Infant Aphakia Treatment Study Group. “Glaucoma-related adverse events at 10 years in the Infant Aphakia Treatment Study: a randomized clinical trial”. Published December 17, 2020, JAMA Ophthalmology.

Provided by National Eye Institute

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